The present invention relates to a device for dilating a pupil and/or maintaining a pupil in a dilated state.
The invention has been developed primarily for use in ophthalmic surgery and will be described hereinafter with reference to this application.
It is advantageous in many ophthalmic procedures for the pupil to be dilated as much as possible, that is for the iris to be retracted toward the outer edges of the eye. This normally occurs automatically when the eye is deprived of bright light, for example, in dark rooms or at night.
When performing ophthalmic operations, such as inserting an intra-ocular contact lens (ICL), in the posterior chamber, a dilated iris and pupil gives the surgeon a larger area to manipulate the ICL into position. The lens in the eye and its enclosing capsule are delicate structures that may be easily damaged by excessive contact pressure and shock. By maximising the area available to the surgeon there is a reduction in the risk of damaging the iris or human lens or other components of the eye due to unintentional contact with the various surgical instruments.
Retinal surgery involves operating on the retina on the back of the eye while occasionally viewing the retina inside the eye through the pupil. Again a large pupil is a definite advantage for the surgeon during this difficult procedure. Accordingly, maximising the dilation of the iris is of great assistance.
Cataract surgery involves replacing the natural human protein lens inside the eye with an artificial lens. This is usually done because the natural lens has degraded over time from the effects of ultra-violet rays and ageing such that the lens is no longer clear.
In some countries, the present procedure for removing the natural lens involves cutting a semicircle around the edge of the cornea of the eye folding back the resultant flap and physically removing the lens from its enclosing capsule through the iris. The lens is then replaced with a new relatively rigid artificial lens, the cornea returned to its original position and sutured into place. Recovery from this procedure is quite slow and the sutures may subsequently need to be removed.
In most Western countries and Japan, a more advanced procedure is performed involving an ultrasonic fractionator instrument known as a phaco-emulsifier. In this technique the pupil is usually dilated using a topical drug in the form of eye drops and an incision about 3 mm wide is made in the periphery of the cornea. The anterior chamber is inflated with a xe2x80x9cvisco-elasticxe2x80x9d material to keep the anterior chamber fully formed and deep. A tool is introduced through this incision to tear away the anterior capsule covering the lens. The phaco-emulsifier is then introduced through the incision and used to break up the lens. The pieces being sucked out by the phaco-emulsifier and any remnants are drawn out by irrigation/aspiration. The new lens made of foldable material is then introduced through the wound and unfolded into place. The visco-elastic is then sucked from the eye and the procedure is complete. Stitching is not necessary and the patient need only stay overnight or may even be able to return home immediately. This technique is much less traumatic to the eye and much less costly in hospital stay and recuperative therapy.
About one in five patients do not achieve sufficient pupil dilation with topical drugs. Also such eye drops can wear off during an operation resulting in the iris contracting and reducing the pupil size during surgery. This complicates the removal of any lens remnants during and after phaco-emulsification as it is not possible to see inside the entire lens capsule when a portion of it is covered by the iris. Without sufficient pupil dilation, removal of the lens remnants is done by xe2x80x9cfeelxe2x80x9d relying heavily on the experience of the surgeon. Experience has shown that thorough capsular xe2x80x9cclean upxe2x80x9d of the remnants significantly reduces the need for secondary clean up procedures following cataract surgery.
Insufficiently dilated pupils are also prone to damage from the tip of the phaco-emulsifier. With a small pupil there is a greater likelihood that the phaco-emulsifier tip will touch the inner edge of the iris during emulsification of the lens and cause permanent damage to the iris structures. This is most likely to occur at the inner edge of the iris diametrically opposed to the incision.
A number of physical and therefore surgically more complicated measures can be used to dilate the pupil and maintain it in a dilated state.
One method involves making four minor incisions at roughly 90xc2x0 intervals around the periphery of the cornea and inserting a small hook-like apparatus through each incision. The hooks engage with the inner circumferential edge of the iris and when retracted, pull the iris outwards to define an enlarged substantially square shaped opening. Another physical method, known as sphincterotomy, involves making an incision into the cornea through which a blade is passed that makes radial cuts into the iris itself, thus allowing the iris to dilate and expose more of the lens. Both the above methods add extra time to the total operation time and the latter involves considerable risk of damage to the patient""s iris. Moreover, the damage done in segmenting the iris during a sphincterotomy is irreversible and results in a permanently disfigured iris.
More recent advancements have included the use of generally annular dilating devices. These are usually made from resilient polymeric materials which are contractible to enable insertion through a small incision in the cornea, sclera or limbus and positioning within the iris, the resilient nature of the material acting upon placement to urge and maintain the iris outwardly into a dilated state. These types of prior art dilating devices can be divided into three separate categories.
The first category comprises dilating devices which in their expanded states generally form a complete annulus having surfaces thereon adapted to engage the inner edge of the iris. Examples of such devices are shown in U.S. Pat. No. 4,782,820 (Woods), U.S. Pat. No. 5,267,553 and 5,322,054 (Graether) and U.S. Pat. No. 4,387,706 (Glass).
The Glass device comprises a complete annular ring having a generally xe2x80x98Lxe2x80x99 shaped cross section defining an inner axial wall and a posterior flange for seating behind the iris. The dilator is deformable via a pair of opposed pinions provided on the posterior flange. These pinions enable the dilator to be compressed to an oval configuration by the use of forceps to facilitate positioning of the device within the pupil. However, given the relatively rigid nature of the flanged structure and the absence of any means to retain the dilator in a direction parallel to the central axis of the iris, it is understood that practical use of this device in terms of both insertion into the anterior chamber of the eye and subsequent location within the iris would be extremely difficult if not impossible. This view is probably supported by the fact that it appears this design did not materialise into a commercially successful form.
The Graether patents then go on to describe a pupil expander that is generally xe2x80x98Uxe2x80x99 shaped in-cross section forming an incomplete annulus, the ends of which are joined by a flexible connecting strap to make a complete circle. In use the expander is deformed into an elongated shape for insertion into the eye via a scieral incision. Elongation is preferably achieved by use of a specially designed jig which aligns the elongated xe2x80x98Uxe2x80x99 shaped side walls for sliding onto special forcep tips. While it appears the xe2x80x98Uxe2x80x99 shaped channel structure goes some way to addressing the iris retainment problem of Glass, its use is still a slow and awkward procedure and necessitates during insertion severe deformation of the iris into a xe2x80x9ccatxe2x80x9d like elongate slit which is potentially damaging to the iris.
Woods teaches what may well have been a further improvement over Glass, describing a device also having an elongated arcuate, flexible, resilient body that is generally xe2x80x9cUxe2x80x9d-shaped in cross section to define an iris receiving side wall, the ends of the body being slidably inter-engaged into a circular ring like structure. A drawstring is provided for manually contracting the body for initial placement within the iris. Arguably the feature of circumferential contraction as opposed to oval deformation may theoretically be advantageous in relation to engaging the device with the iris. However, it is believed that the manufacture and operation of such a device incorporating a draw string contracting mechanism would be extremely difficult, and that its use during ophthalmic procedures would be time consuming and not necessarily reliable. For example the difficulties associated with insertion into the anterior chamber of the eye have not been addressed and nor have means been described for ensuring accurate positioning of the heavily flanged and thereby reasonably rigid device into full engagement with the inner peripheral edge of the iris. Again there does not appear to have been any successful commercialisation of the Woods device to date.
The second category comprises resilient devices that are not fully circular in plan but are generally xe2x80x9cUxe2x80x9d or xe2x80x9cCxe2x80x9d-shaped thereby defining an incomplete annulus or similar shape. Examples of such devices include that described in U.S. Pat. No. 5,163,419 (Goldman) and a commercially available pupil dilating device known as the xe2x80x9cSchlosshardtxe2x80x9d design produced by xe2x80x9cMorscherxe2x80x9d.
The Goldman device is generally xe2x80x9cUxe2x80x9d-shaped in plan and can be considered to comprise two separate arm portions connected by an intermediate hinge section. The hinge section enables folding of the device for insertion through a corneal incision and for contraction of the device for placement within the pupillary opening. Iris engaging slots or channels are provided at the hinge and the distal ends only of the two arm members. It is believed this would be hard to accurately engage with the iris and further would be readily prone to dislodgment due to fluctuations of pressure that occur during phaco-emulsification.
Similarly, the Morscher Schlosshardt design is generally xe2x80x9cCxe2x80x9d-shaped in plan, again having iris engaging and retaining formations only at selected spaced intervals around the periphery. Both of the devices include various instrument engaging formations to enable contraction of the device.
The open ended nature of these second category of dilator devices, or at least the Morscher design, may possibly enable easier insertion via the corneal or scleral incision, in that devices could in theory be xe2x80x98dialledxe2x80x99 into the anterior chamber of the eye without the need for prior folding or deformation of the device to facilitate insertion. However, once these devices are in the anterior chamber of the eye, two or more instruments are required for accurate placement and positioning of the device within the pupillary opening. Commercial videos demonstrating use of the Morscher device show that time and dexterity is required for successful manipulation of these devices and that the usual procedure is to rotate the dilator into the iris. This tends to apply a shear force to the iris causing substantial deformation and risk of damage.
The third group includes that described in the applicant""s earlier application WO 96/29965 which describes therein various embodiments of devices all comprising a resilient generally arcuate body portion adapted to engage and retain the iris in a dilated state, from the open ends of which two integrally formed positioning arms extend generally radially outwardly. The arms are sized so that the distal ends of the arms during the operation remain external to the eye. In use, the two armed ring is folded or otherwise compressed for insertion through the incision in the cornea, after which the arms are manipulated externally to help in the positioning of the body portion within the pupillary opening. This can be assisted with the aid of suitable additional instruments such as Fenzl hooks and the like.
The addition of the positioning arms was found to greatly assist the process of insertion and removal from the iris and general handling of the device during the operation. However, problems were still encountered during the practical implementation of the design in relation both to the initial insertion of the device into the eye and the subsequent manipulation of the device into position in the iris.
In summary therefore there is still a need for an improved dilator device that is easy and fast to use, offers minimum risk of damage to the eye and is reliable in that its performance is predictable and consistent.
It is an object of the present invention to provide a device for dilating a pupil and/or maintaining a pupil in a dilated state which overcomes or ameliorates one or more of the deficiencies of the prior art or at least offers useful alternative thereto.
According to the invention there is provided a pupil dilating device for dilating a pupil and/or maintaining a pupil in a dilated state, said device being generally hooked shaped in plan view so as to define an open ended arcuate iris engaging body portion having a distal free end, and at or adjacent the other of said ends an integral positioning arm extending outwardly in a generally radial direction therefrom, the positioning arm being sized to extend in use beyond the outer periphery of the iris, said body portion including an iris engaging formation or formations being adapted to engage and retain the inner peripheral edge of an iris in an expanded state and at least one instrument engaging formation at or adjacent said distal free end to enable contraction of the body portion to facilitate engaging location within the iris.
In this manner the pupil dilating device according to the invention provides an instrument which can be easily inserted into the anterior chamber of the eye by xe2x80x98diallingxe2x80x99 through an incision in the cornea sclera or limbus, the integral arm providing remote means for assisting in the xe2x80x9cdiallingxe2x80x9d in procedure and subsequent positioning and removal of the device from the pupil. The arm also provides means for securing the device in the preferred location and, if necessary, convenient means for rotating the dilator to a preferred orientation to enable unobstructed access for the various surgical instruments as required.
In preferred forms, the iris engaging formation or formations extend along a majority of the arcuate body portion.
Preferably, the body portion includes additional instrument engaging formations including, in particular, one such formation located at or adjacent the join between the body portion and the integral positioning arm.
Desirably, the iris engaging formations are provided by a body portion that is generally xe2x80x9cUxe2x80x9d-shaped in cross section along all or at least at regular intervals around its periphery, the materials and wall thicknesses ideally being selected to ensure adequate flexibility.
Preferably the body portion and/or engaging formations extend circumferentially to define an included angle of between 270xc2x0 and 320xc2x0.
Desirably, the instrument engaging formations comprise fenestrations formed in an upper or anterior surface of the body portion which are adapted to receive and incorporate suitable positioning instruments such as xe2x80x9cSinskeyxe2x80x9d or xe2x80x9cFenzlxe2x80x9d hooks or the like.
Unless the context clearly requires otherwise, throughout the description and the claims, the words xe2x80x98comprisexe2x80x99, xe2x80x98comprisingxe2x80x99, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of xe2x80x9cincluding, but not limited toxe2x80x9d.
In preferred forms of the invention, the positioning arm is sized to extend in use not only beyond the outer periphery of the iris, but to a position external to the eye itself, and more preferably includes a fixation point at or adjacent its distal end. Desirably, the positioning arm is curved to correspond with the contours of the relevant parts of the eye between the external curvature of the globe and the pupillary opening.
In some embodiments, it will be convenient to include a structure at the distal end of the arm to prevent the distal end of the arm from entering the wound.
It is further preferred that the iris engaging formations of the body portion comprise anterior and posterior flanges connected by an intermediate central wall or bight portion. More preferably, one or both of these flanges are scalloped to provide additional flexibility and assist in the engagement with the iris.
In some preferred embodiments, the posterior flange is more soft and supple than the anterior flange. In these embodiments the relatively supple posterior flange may be co-molded from a suitable soft material A suitable soft material is typically a biocompatible smooth material with a hardness about Shore 65A whereas the remainder of the body portion material has a hardness of about Shore 95D. Instead of co-molding, the posterior flange may be coated with a suitable soft material such as silicone or subject to a surface softening treatment such as chemical or plasma surface modification. Alternatively, the entire body portion or device may be coated with soft material. It is also envisaged that the device may be formed from a suitably soft material with an insert or other reinforcing element providing the necessary rigidity.
Embodiments using a relatively soft posterior flange provide significant benefits during procedures such as non-cataract surgery wherein the existing lens may be clear and inappropriate for removal but unable to focus adequately. The surgical insertion of an intra-ocular contact lens into the posterior chamber in front of the natural lens to correct the defect is not undertaken today if the pupil does not dilate with drugs to at least a 5 mm diameter. The present device can be used to sufficiently dilate the iris and in these particular cases, it is important to minimise trauma to the lens and capsule caused by the dilator. A relatively soft posterior flange helps to ensure this while the rest of the body portion is sufficiently rigid to maintain the pupil in a dilated state.
It is further preferred that the device be constructed so as to have a specific gravity equal to or less than balanced salt solutions so that in use it will not xe2x80x9cweigh downxe2x80x9d the iris.